Bonding of Materials with Induction Heating

ABSTRACT

An apparatus and process are provided for forming a two-metal flat bonded article. A flat metal sheet in solid form is placed in the indention of a heat resistant plate. A second heat resistant plate is placed over the flat metal sheet in the indentation to form a flat metal sheet enclosure. The flat metal sheet enclosure is placed in a U-shaped inductor assembly embedded with a solenoidal induction coil. Supply of alternating current to the solenoidal induction coil inductively heats the flat metal sheet after which the sheet is withdrawn from the inductor assembly. The second heat resistant plate is removed and a bond metal in liquid form is placed over the top surface of the flat metal sheet in the indentation so that the two-metal flat bonded article is formed as the bond metal solidifies.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of application Ser. No. 11/735,098, filed Apr. 13, 2007, which is a divisional application of application Ser. No. 10/615,150, filed Jul. 8, 2003, now U.S. Pat. No. 7,205,516, which claims the benefit of U.S. Provisional Application No. 60/394,515, filed Jul. 9, 2002, all of which are hereby incorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to the use of magnetic induction heating of a material to bond multiple materials together.

BACKGROUND OF THE INVENTION

Bonded materials are used in many applications. For example, a slide bearing may be formed from a bonded composition that consists of a metal backing plate and a bearing surface material that is bonded to the plate. The bearing surface material may be a metal composition such as a copper or an aluminum alloy. Slide bearings are linear or rotary in form. Linear slide bearings are in sheet form, whereas rotary slide bearings are in cylindrical or half-cylindrical form. Half-cylindrical slide bearings are used in pairs for applications such as journal bearings in internal combustion engines.

One method of producing slide bearings involves a continuous process line wherein the feedstock for the metal backing plate is a continuous roll of sheet steel. The continuous roll of sheet steel is fed through heat treating furnaces and further conditioned before the bearing surface material is applied to it. Raised edge lips are formed on the longitudinal edges of the continuous sheet and the bearing surface material, in a liquid form, such as a molten copper or aluminum alloy, is poured onto the sheet. The molten alloy solidifies and is bonded to the sheet, and can be quench treated. Subsequent milling controls the thickness of the bearing surface material. The sheet is cut into desired sizes for slide bearing applications. For rotary slide bearings, the cut pieces are further formed into a cylindrical shape. Economically, the process must operate as an uninterrupted line process, since stopping the line and restarting the line involves a substantial effort in repeatedly bringing the line's furnaces to operating temperature. Therefore there exists the need for a method of bonding metals in a batch process for applications such as slide bearings.

BRIEF SUMMARY OF THE INVENTION

In one aspect, the present invention is an apparatus for, and method of, producing a bonded pair of metal sheets. A flat metal sheet is seated in solid form in an indentation in a first heat resistant plate. The indentation has a perimeter substantially equal to the perimeter of the flat metal sheet. A second heat resistant plate is seated over the first heat resistant plate that contains the flat metal sheet so that an interior protruding region of the second heat resistant plate seats in the indentation in the first heat resistant plate over the top surface of the flat metal sheet, with the combination of the second heat resistant plate seated over the first heat resistant plate forming a flat metal sheet container. The flat metal sheet container is inserted into a side-entry interior volume of a U-shaped inductor assembly having at least one solenoidal induction coil embedded in the top and bottom of the U-shaped inductor assembly. The side-entry interior volume has a height substantially equal to the height of the flat metal sheet container to press the interior protruding region of the second heat resistant plate over the top surface of the flat metal sheet. Alternating current is supplied to the at least one solenoidal induction coil to inductively heat the flat metal sheet. The heated flat metal sheet container is withdrawn from the side-entry interior volume of the U-shaped inductor assembly. The second heat resistant plate is removed from the first heat resistant plate and a bonding metal in liquid form is placed over the top surface of the flat metal sheet, after which the bonding metal is allowed to bond to the flat metal sheet as it solidifies.

These and other aspects of the invention are set forth in this specification and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures, in conjunction with the specification and claims, illustrate one or more non-limiting modes of practicing the invention. The invention is not limited to the illustrated layout and content of the figures in the drawings.

FIG. 1 is an isometric view of one example of an apparatus of the present invention for bonding materials with induction heating.

FIG. 2 is an isometric view illustrating one example of an arrangement of induction coils for the apparatus shown in FIG. 1.

FIG. 3 is a front elevational view of the apparatus shown in FIG. 1.

FIG. 4 is a side elevational view of the apparatus shown in FIG. 1.

FIG. 5 is a top view of the apparatus shown in FIG. 1, further illustrating the arrangement of induction coils shown in FIG. 2.

FIGS. 6( a), 6(b) and 6(c) illustrate another example of the present invention for bonding materials with induction heating.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, wherein like numerals indicate like elements, there is shown in FIG. 1 through FIG. 5, one example of apparatus 10 of the present invention for bonding of materials with induction heating. Apparatus 10 includes first induction heating plate 12, frame 14 and second induction heating plate 16. First and second induction heating plates 12 and 16, and frame 14, are formed from a heat resistant, non-electrically conductive material, such as a ceramic composition. First plate induction coil 18 is disposed in first induction heating plate 12; frame induction coil 20 is disposed in frame 14; and second plate induction coil 22 is disposed in second induction heating plate 16. When a castable material, such as a ceramic composition, is used for the heating plates and frames, the coils may be embedded in the heating plates and frame during the casting process.

The induction coils are arranged to form a transverse induction coil assembly for inductively heating an electrically conductive sheet 90 placed between the first induction heating plate, and the combination of the frame and second induction heating plate when the second induction heating plate is inserted into the frame. While the sheet is generally referred to as a metal sheet, any electrically conductive material may be used. The particular arrangement of coils shown in the figures illustrates one non-limiting example of transverse flux coil arrangements that can be used in the present invention. The illustrated induction coils may be fluid (liquid or gas) cooled by circulation of a cooling fluid, such as water, through hollow induction coils or separate cooling coils in the heating plates and frame. In some examples of the invention, an induction coil may not be necessary in frame 14.

Metal sheet 90 is placed upon the top surface of first induction heating plate 12. The dimensions of metal sheet 90 are such that when frame 14 is placed over the top surface of first induction heating plate 12, the perimeter of the metal sheet will extend beyond the interior open space in frame 14 to establish a metal sheet contact surface around the metal sheet's perimeter that is sandwiched between the top surface of the first induction heating plate 12 and the bottom surface of frame 14.

With metal sheet 90 positioned on the surface of first induction heating plate 12, as described above, frame 14 and second induction heating plate 16 are placed over the top surface of the first induction heating plate 12 and the metal sheet. The interior open space in frame 14 is sized to allow the fitting of second induction heating plate 16 so that the bottom surface of the second induction heating plate 16 makes contact with metal sheet 90. With the frame and second induction heating plate placed over metal sheet 90, suitable ac current is supplied from one or more power sources to first plate induction coil 18, frame induction coil 20, and second plate induction coil 22. The magnetic field created by ac current flow in the first plate induction coil 18 inductively penetrates and heats into the facing side of metal sheet 90, whereas the magnetic fields created by ac current flow in the frame induction coil and second plate induction coil inductively penetrate and heat into the opposing side of the metal sheet. As best illustrated in FIG. 5, the orthogonal orientation of the first plate induction coil to the combination of the frame and second plate induction coils provides a crisscross induction heating pattern that enhances uniform heat penetration of the sheet. Pressing the metal sheet between the first and second induction heating plates prevents surface distortion of the sheet as it is heated.

When metal sheet 90 has been inductively heated to a desired temperature, second induction heating plate 16 is raised at least a sufficient distance to allow pouring of a molten metal composition, such as a copper or aluminum alloy, onto the top surface of the heated metal sheet. The temperature of the metal sheet may be sensed by one or more sensors, such as contact thermocouples embedded in the first and/or second induction heating plates to determine when the sheet has been heated to the desired temperature. For example, if the metal sheet is steel, it is heated to approximately 2,100° F. for casting of a molten alloy, such as bronze, onto its surface. While the term “molten metal” or “molten alloy” is used, any liquid material capable of bonding with the heated electrically conductive sheet may be used. Frame 14 remains in place to hold the metal sheet flat and to provide a dam for the molten metal composition. The molten metal may be ported through one or more openings in frame 14, or poured, into the interior open space in frame 14 which was previously occupied by the second induction heating plate. After pouring a quantity of molten metal over the top surface of the metal sheet, the metal will bond with the sheet as it cools. Alternatively, the metal can be quenched by injecting a quench fluid or gas into the interior open space in the frame over the top surface of the cooled molten metal. The quench material may be ported through one or more openings in frame 14, or poured, into the interior open space in frame 14. The now solidified molten metal is bonded to the metal sheet to form a bonded metal product, and frame 14 can be removed from over the top surface of first induction heating plate 12. The interior surface wall of frame 14 may be skewed towards its outer wall in the region where the molten metal is poured to facilitate removal of the frame. Additionally the same region of the wall may be specially treated with a coating that will inhibit bonding of the molten metal to the wall of the frame. By way of example, and not limitation, a typical range of thickness of the metal sheet is approximately 3.5 to 19 mm, and a typical range of thickness of the cast metal on the metal sheet is approximately 2.5 to 5.0 mm. Further working of the product can include milling for thickness control of the product. If the product is used as slide bearings, the product is appropriately cut to the desired dimensions. For rotary slide bearings, the cut product is then worked to a cylindrical shaped.

In an alternative embodiment of the invention, the top surface of first induction heating plate 12, rather than being flat, is indented for an area approximately equal to the surface area of the bottom surface of second induction heating plate 16. In this arrangement, after metal sheet 90 has been heated, the second induction heating plate can be moved towards the metal sheet to apply sufficient pressure on the heated sheet to force it into the indentation in the first induction heating plate. In this example, the frame does not generally provide a dam for the molten metal composition that is poured over the top of the sheet since the raised edges of the indented metal sheet and/or the walls of the indentation will serve as a dam for the molten metal composition. In this example of the invention, the frame serves as a means for holding the metal sheet in place during induction heating and molten metal pour after the sheet is pressed into the indentation in the first induction heating plate.

In other examples of the invention longitudinal flux coils, such as solenoidal coils, may be utilized. For example, as illustrated in FIG. 6( a), solenoidal induction coil 21 is disposed in inductor assembly 23. Metal sheet 90 is inserted into indentation 25 in first heat resistant plate 13. Second heat resistant plate 17 is placed over the first ceramic plate and the enclosed metal sheet is inserted into inductor assembly 23 as shown in FIG. 6( b) wherein it is inductively heated by a magnetic field established when as current flows through coil 21. After the metal sheet reaches the desired temperature, the enclosed metal sheet is removed from the inductor assembly, and the second heat resistant plate is removed, as shown in FIG. 6( c), so that the molten metal can be poured over the metal sheet in the indentation.

The foregoing examples do not limit the scope of the disclosed invention. The scope of the disclosed invention is further set forth in the appended claims. 

1. A method of bonding the adjacent sides of a pair of metal sheets, the method comprising the steps of: seating a flat metal sheet in solid form in an indentation in a first heat resistant plate, the indentation having a perimeter substantially equal to the perimeter of the flat metal sheet; seating a second heat resistant plate over the first heat resistant plate containing the flat metal sheet so that an interior protruding region of the second heat resistant plate seats in the indentation in the first heat resistant plate over the top surface of the flat metal sheet, the combination of the second heat resistant plate seated over the first heat resistant plate forming a flat metal sheet container; inserting the flat metal sheet container into a side-entry interior volume of a U-shaped inductor assembly having at least one solenoidal induction coil embedded in the top and bottom of the U-shaped inductor assembly, the side-entry interior volume having a height substantially equal to the height of the flat metal sheet container to press the interior protruding region of the second heat resistant plate over the top surface of the flat metal sheet; supplying alternating current to the at least one solenoidal induction coil to inductively heat the flat metal sheet; withdrawing the heated flat metal sheet container from the side-entry interior volume of the U-shaped inductor assembly; removing the second heat resistant plate from the first heat resistant plate; placing a bond metal in liquid form over the top surface of the flat metal sheet; and bonding the bond metal to the top surface of the flat metal sheet as it solidifies.
 2. Apparatus for bonding the adjacent sides of two metal sheets together, the apparatus comprising: a U-shaped inductor assembly having a side opening into the interior volume of the U-shaped inductor assembly; at least one solenoidal induction coil embedded in at least the top and bottom of the U-shaped inductor assembly; at least one alternating current power supply connected to the at least one solenoidal induction coil; and a flat metal sheet containment enclosure comprising a first and second heat resistant plate, the first heat resistant plate having an indentation with sufficient height for at least seating the flat metal sheet in solid form in the indentation and a bonding metal in liquid form over the flat metal sheet, the second heat resistant plate having an interior protruding region, the interior protruding region removably insertable into the indentation to a depth sufficient to touch the top surface of the first metal sheet when seated in the indentation, the interior volume of the U-shaped inductor assembly having a height substantially equal to the height of the combination of the first and second heat resistant plates when the interior protruding region of the second heat resistant plate is inserted into the indentation of the first heat resistant plate.
 3. The apparatus of claim 2 wherein the first and second heat resistant plates are formed from a ceramic composition.
 4. A two-metal flat bonded article formed from a process comprising the steps of: seating a flat metal sheet in solid form in an indentation in a first heat resistant plate, the indentation having a perimeter substantially equal to the perimeter of the flat metal sheet; seating a second heat resistant plate over the first heat resistant plate containing the flat metal sheet so that an interior protruding region of the second heat resistant plate seats in the indentation in the first heat resistant plate over the top surface of the first flat metal sheet, the combination of the second heat resistant plate seated over the first heat resistant plate forming a flat metal sheet container; inserting the flat metal sheet container into a side-entry interior volume of a U-shaped inductor assembly having at least one solenoidal induction coil embedded in the top and bottom of the U-shaped inductor assembly, the side-entry interior volume having a height substantially equal to the height of the flat metal sheet container; supplying alternating current to the at least one solenoidal induction coil to inductively heat the first flat metal sheet; withdrawing the first flat metal sheet container from the side-entry interior volume of the U-shaped inductor assembly; removing the second heat resistant plate from the first heat resistant plate; placing a second metal in liquid form over the top surface of the first flat metal sheet; and bonding the bond metal to the top surface of the flat metal sheet as it solidifies. 